# Precision cosmology with baryons: non-radiative hydrodynamics of galaxy groups

## TL;DR

This study investigates the impact of non-radiative hydrodynamics on galaxy group structures, providing high-resolution simulations that improve understanding of baryonic effects on the matter power spectrum relevant for future cosmological surveys.

## Contribution

It offers detailed high-resolution simulations of galaxy groups under non-radiative hydrodynamics, analyzing their mass and gas profiles and developing predictive models with high accuracy.

## Key findings

- Total mass profile fits NFW model with slight modifications.
- Gas profiles are well approximated by the Komatsu & Seljak hydrostatic solution, with deviations.
- Predictive models for gas density and temperature profiles achieve better than 20% accuracy.

## Abstract

The effect of baryons on the matter power spectrum is likely to have an observable effect for future galaxy surveys, like Euclid or LSST. As a first step towards a fully predictive theory, we investigate the effect of non-radiative hydrodynamics on the structure of galaxy groups sized halos, which contribute the most to the weak lensing power spectrum. We perform high resolution (more than one million particles per halo and one kilo-parsec resolution) non-radiative hydrodynamical zoom-in simulations of a sample of 16 halos, comparing the profiles to popular analytical models. We find that the total mass profile is well fitted by a Navarro, Frenk & White model, with parameters slightly modified from the dark matter only simulation. We also find that the Komatsu & Seljak hydrostatic solution provides a good fit to the gas profiles, with however significant deviations, arising from strong turbulent mixing in the core and from non-thermal, turbulent pressure support in the outskirts. The turbulent energy follows a shallow, rising linear profile with radius, and correlates with the halo formation time. Using only three main structural halo parameters as variables (total mass, concentration parameter and central gas density), we can predict with an accuracy better than 20% the individual gas density and temperature profiles. For the average total mass profile, which is relevant for power spectrum calculations, we even reach an accuracy of 1%. The robustness of these predictions has been tested against resolution effects, different types of initial conditions and hydrodynamical schemes.